“Abstract: Targeted drug delivery systems are ideal technology to increase the maximum mechanism of action with smaller dose, we have developed miltefosine encapsulated PLGA–PEG nanoparticles (PPEM) to target macrophage of infected tissues against Leishmania donovani. The structural characterization of PLGA–PEG by transmission electron microscopy (TEM) has shown a size range of 10 to 15 nm. Synthesis and drug encapsulation confirmed by dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR) and confirmed NP encapsulation. The dose of nano encapsulated miltefosine decreased by fifty percent as compared to that of a conventional miltefosine and Amphoterecin B. The inhibition of amastigotes in the splenic tissue with nano encapsulated miltefosine (23.21 ± 23) was significantly more than the conventional miltefosine (89.22 ± 52.7) and Amphoterecin B (94.12 ± 55.1). This study signifies that there is an increased contact surface area of the nano encapsulated drug and significant reduction in size, improved the efficacy in both in vitro and in vivo study than that of the conventional miltefosine, Amphoterecin B. Graphical abstract: The analyses of detailed structure characterized by TEM and DLS confirmed the nano-size of the particle 10–20 nm and FTIR confirmed for antileishmanial drug encapsulation in to PLGA–PEG. The dose of miltefosine is decreased by fifty percent as the IC50 value is decreased from 0.2 to 0.1 μg. Further inhibitions of amastigotes in the splenic tissue with these nanoparticles are significantly more than the conventional miltefosine and PLGA–PEG encapsulated Amphoterecin B (23.21 ± 23/89.09 ± 52.7/92.12 ± 55.1). Keywords: Miltefosine; Transmission electron microscope; Nanoscale; Amastigotes; Amphoterecin B"